The present invention relates to a magnetic head used for writing and reading to and from a magnetic recording medium and a magnetic recording apparatus mounting the magnetic head.
In a magnetic disk apparatus, data on a recording medium is written and read by a magnetic head. For increasing the recording capacity of a magnetic disk per unit area, it is necessary to increase the areal density. However, the current longitudinal recording system involves a problem that the areal density cannot be increased due to thermal fluctuation of magnetization of a magnetic medium as the recorded bit length is smaller. A method capable of overcoming the problem includes a perpendicular recording method of recording magnetization signals in the direction perpendicular to the magnetic medium. The perpendicular recording system can use a giant magneto-resistive head (GMR head), a tunneling magneto-resistive head (TMR head) having higher read output and a CPP (current perpendicular to the plane) type GMR head of flowing current perpendicular to the film plane for reading. On the other hand, it is necessary to use a single pole head for writing. Also in the perpendicular recording, it is necessary to improve the track density and the linear recording density in order to improve the longitudinal recording density. In order to improve the linear recording density, it is necessary to improve the recording magnetic field gradient of the recording head. For this purpose, a dual layered structure is adopted for a recording medium in which a soft underlayer (SUL) is disposed as a lower layer. However, for attaining higher recording density above 200 Gb/in2, further improvement of the magnetic field gradient from the recording head is also necessary. Moreover, for improving the track density, the track width of the magnetic head has to be made finer and more accurate. However, as the track is made narrower, a problem that an effective track width to be written into a magnetic medium is larger than the geometric track width becomes conspicuous and this imposes a significant restriction on the improvement of the track density. For overcoming the problem, U.S. Patent Publication No. 2002/0176214A1 or “The Magnetic Recording Conference (TMRC) 2003” (abstract No. E6), for example, disclose an example of a perpendicular recording head provided with a side shield as shown in FIG. 20. A view from an air bearing surface (ABS) is shown on the left and a cross-sectional view perpendicular to the air bearing surface is shown on the right of FIG. 20. A read head is also shown in the drawing.
The documents described above state that a side shield is provided for controlling the track width to be written into a magnetic medium, but the gap distance on the trailing side is larger than the gap distance on the side, and the recording magnetic field gradient which is important in the recording process together with the magnetic field intensity is insufficient. Further, while the magnetic field intensity decreases greatly when the side shield is provided, a structure for not decreasing the magnetic field intensity is insufficient.